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Erin Kiernan’s infant used to sleep like a dream until he started teething. Earlier this week, the cranky 6-month-old kept his mother up all night, drooling and spitting up on her whenever possible.

“I used to think I knew what exhausted was. Hilarious,” the Iowa news anchor wrote in a Facebook caption of a selfie she posted showing her looking bleary-eyed and bespectacled, sans makeup and hair pulled back.

Hundreds of viewers and followers applauded Kiernan for sharing a “real mom moment” and offered her words of support.

But in addition to the encouragement, Kiernan also received snide comments about her appearance. One particularly nasty note from someone who told her, among other things, “this doesn’t even look like the same person!” made her snap.

“I just kind of lost it. And then I thought, this is ridiculous, I am not this object that people see on TV all the time,” she told TODAY.

So Kiernan fought back.

She responded to the “snarky message” she received by posting side-by-side photos of her anchor headshot next to the picture she had posted a day earlier of herself looking exhausted.

“Newsflash! These ARE NOT pictures of the same person. The woman on the left is well rested, spent two hours on her hair and makeup, had a professional photographer take her picture (and Photoshop it, I'm sure), and is in the ‘glowing’ second trimester of pregnancy,” she wrote.

“The woman on the right got two hours of sleep (maybe), hadn't looked in the mirror, took a selfie, did not put a filter on it and is covered with spit up and drool from a teething and very crabby baby,” she continued. “You are an idiot if you think these are pictures of the same woman. #truth#reallife”

The post received more than 10,000 likes, 250 shares and more than three times as many supportive comments as her original post.

“There is exhaustion and then there is Mom exhaustion,” Maureen Carlon O’Hara wrote on the post. “And yes anybody who made snarky comments is an idiot, and probably never worked on three hours of sleep, none of which were in a row.”

Crystal White Rhoads commended Kiernan for her honesty and said, "I think a picture of a mommy in the trenches is simply beautiful."

Kiernan now laughs about the mood she found herself in when responding to the "snarky" note.

“It was really out of character. It’s best described as a product of sleep deprivation,” she told TODAY.

As a public figure, Kiernan said she is used to getting comments criticizing her looks, particularly from people trying to hide behind fake email or social media accounts.

"Typically, I ignore those things. I don’t direct message them back. I certainly don’t call them out," she said. "But there can be a cumulative effect when you get a number of them from people I characterize as snarky. We all have a breaking point. Again, I blame sleep deprivation."

Kiernan said she's been deeply touched by the comments people have left on her post and has tried her best to respond to every one.

“It means a lot to me, and it makes me a little bit emotional because it reinforces that you’re not alone," she said. "Whether you're a mother or not, just as women, as people, a lot of times we feel that life is hard. No one’s life is this shiny, perfect existence.”

Kiernan said her son is normally “really easy and happy,” but lately his teething has left the baby “drooling like crazy and chewing on everything.”

“We are spoiled as parents, and that’s also probably why I was so out of my mind,” she said about how she felt earlier this week. "We really haven’t experienced the sleepless night thing since he was itty bitty.”

"I'm just so grateful to be a mom. It took my husband and I years and years to make this happen," she said. "I love being a mom, even when it’s exhausting and frustrating and I'm out of my mind. And I love my job, too. I’m grateful for both.”